This invention relates to the field of medical devices, and more particularly to a guide wire for advancing a catheter within a body lumen in a procedure such as percutaneous transluminal coronary angioplasty (PTCA).
In a typical PTCA procedure, a guiding catheter having a pre-formed distal tip is percutaneously introduced into a patient's peripheral artery, e.g. femoral or brachial artery, by means of a conventional Seldinger technique and advanced therein until the distal tip of the guiding catheter is seated in the ostium of a desired coronary artery. A guide wire is first advanced by itself through the guiding catheter until the distal tip of the guide wire extends beyond the arterial location where the procedure is to be performed. Then a catheter is mounted onto the proximal portion of the guide wire which extends out of the proximal end of the guiding catheter which is outside of the patient. The catheter is advanced over the guide wire, while the position of the guide wire is fixed, until the operative element on the catheter is disposed within the arterial location where the procedure is to be performed. After the procedure is performed, the catheter may be withdrawn from the patient over the guide wire or the guide wire repositioned within the coronary anatomy for an additional procedure.
Conventional guide wires for angioplasty, stent delivery, atherectomy and other intravascular procedures usually have an elongate core member with one or more segments near the distal end thereof which taper distally to smaller cross sections. A flexible body member, such as a helical coil or a tubular body of polymeric material, is typically disposed about and secured to at least part of the distal portion of the core member. A shaping member, which may be the distal extremity of the core member or a separate shaping ribbon which is secured to the distal extremity of the core member, extends through the flexible body and is secured to the distal end of the flexible body by soldering, brazing or welding; or an adhesive may be used in the case of polymeric flexible bodies which forms a rounded distal tip. The leading tip is highly flexible and will not damage or perforate the vessel. The portion behind the distal tip is increasingly stiff, which better supports a balloon catheter or similar device.
A major requirement for guide wires is that they have sufficient column strength to be pushed through a patient's vascular system or other body lumen without kinking. However, they must also be flexible enough to avoid damaging the blood vessel or other body lumen through which they are advanced. Efforts have been made to improve both the strength and flexibility of guide wires to make them more suitable for their intended uses, but these two properties are for the most part diametrically opposed to one another in that an increase in one usually involves a decrease in the other.
In order to fulfill these requirements, guide wires now include two different types of material joined together with a connecting tube so that a proximal core will consist of a material having sufficient column strength and a distal core will be made of a flexible material to advance through a body lumen. Currently, an expensive nitinol hypotube or connecting tube is used to join a proximal stainless steel core to a nitinol distal core on certain types of guide wires. An example of this type of guide wire can be seen in, for example, U.S. Pat. No. 6,248,082 (Jafari).